In recent years, considerable attention has been directed toward improving vehicle performance in the event of collisions or other impacts. One particular aspect that has been addressed has been roof crush resistance. An object of such efforts has been to increase the loads that a vehicle roof is able to withstand (e.g., during a rollover accident) and to help thereby prevent intrusion of the roof into the passenger compartment. Efforts so far largely have been in the area of metal reinforcement, such as the increased use of steel structures for reinforcement. Unfortunately to perform an effective job of structural reinforcement relatively heavy structures are needed. This has an undesired effect of increasing vehicle weight, with an attendant decrease in fuel efficiency. Thus, there is a need for structural reinforcements that provide enough support to meet the need for roof crush resistance, and other structural reinforcement applications, while avoiding the detrimental effects of increasing the weight of the vehicle roof.
In various other vehicle location, recent years have seen the increased use of structural reinforcements in which vehicle cavities are commonly fitted with structural reinforcements that aid in controlling deformation from an impact. For some applications, it has become popular in recent years to employ a carrier structure in combination with an expandable material as part of the reinforcement. See e.g., U.S. Pat. Nos. 6,932,421; 6,921,130; 6,920,693; 6,890,021; and 6,467,834 all incorporated by reference. Typically, these carrier structures are made solely of molded polymeric materials. Some are made solely of metallic materials. As has been the case for a wide number of applications of these structures, the size and geometry of the structure may be related to the extent of load bearing that is required for the application. Often, this has been addressed by simply increasing the amount of material used for the carrier (and thus the part weight) in response to the increased need for impact resistance. Attention to controlling multiple modes of deformation within a single carrier is often only incidental, if at all.
The reinforcement and support of vehicle roof structures provides a further particular challenge, especially in view of the cavity volumes in which reinforcement of the above type is possible. By increasing the amount of material used for the carrier, it may be difficult to employ a reinforcement that is large enough to provide the requisite support but small enough to fit within the confines of certain vehicle cavities, including pillars and door sills. In addition, many new vehicle designs, particularly those related to compact vehicles, require stronger reinforcements in even smaller cavities. Traditional reinforcement structures may not be suitable, as cavity size requirements often limit the ability to add more material to the reinforcements for strength increase.
Thus, there remains a need for alternative techniques that allow for the ability to improve the support capability of a carrier while avoiding the addition of substantial weight and further avoiding the expense and time associated with additional raw materials and additional processing time. There also remains a need for a structural reinforcement that can be made in a relatively low profile shape so that it can be employed with success in smaller cavities.